Loader



Oct. 29, 1957 Filed Feb. 7, 1956 E. B. WAGNER LOADER 3 Sheets-Sheet 1 IN V EN TOR.

EDDIE B. WAGNER Arrow/5m Oct. 29, 1957 E. B. WAGNER LOADER 3 Sheets-Sheet 2 Filed Feb. 7, 1956 NR wk MS mdz - INVENTOR. EDDIE B. WAGNER ATTORNEYS Oct. 29, 1957 E. B. WAGNER LOADER 5 Sheets-Sheet 5 Filed Feb. 7. 1956 INVENTOR. EDDIE B'. WAGNER A TTORNEVS United States PatentO LOADER Eddie B. Wagner, Portland, reg., assignor to Mixermobile Manufacturers, Inc., Portland, 0reg., a corporation of Oregon Application February 7, 1956, Serial No. 563,981

8 Claims. (Cl. 214-140) This invention relates to a loader and more particularly to an improved bucket or scoop supporting and actuating mechanism adapted for mounting upon a selfpropelled vehicle.

In the preferred embodiment, the loader of the present invention includes a boom having a bucket supporting structure pivotally mounted at its extended end and carrying a bucket which is pivotally movable relative to the bucket supporting structure. A plurality of power means, such as hydraulic actuators, are employed to raise and lower the boom, to pivot the bucket supporting structure relative to the boom and to pivot the bucket relative to the bucket supporting structure. The arrangement of the boom, bucket supporting structure and bucket are such that the scoop or bucket may be employed to dig or load material at a position even below the supporting surface for the vehicle carrying the boom and bucket, while at the same time enabling the bucket to be elevated to a relatively high position and dumped at such position. The bucket may be inverted and also brought to an upright position in any position in any position of the boom, from its lowest to highest position, and automatic means are provided for preventing the bucket from being tipped from an uprightposition toward the vehicle when the bucket is being raised from a lower to a higher position. Such tipping of the bucket is automatically prevented although the bucket may be tipped away from the vehicle at any time it is desired to do so, for example, for loading or for dumping the bucket. I

It is therefore an object of the present invention to provide an improved loader in which a scoop or bucket may be loaded at a relatively low elevation with respect to the supporting surface for the loader, while at the same time, the bucket may be elevated to a relatively high elevation and dumped.

Another object of the invention is to provide a loader having an improved mounting for the bucket or scoop which enables the bucket to be moved to an upright position after being tipped or inverted for loading at a lower position and to be maintained in such upright position while being raised to an upper carrying or dumping position.

A further object of the invention is to provide an improved loader in which power actuating means are provided between a boom and a bucket supporting structure for pivoting the bucket supporting structure relative to the boom and the power actuator is controlled so as to prevent tipping of the bucket from an upright position toward the vehicle upon which the boom is mounted.

A still further object of the invention is to provide an improved loader having aboom and bucket mounted thereon in which the bucket may be loaded in any one of a variety of positions, including one in which the bucket is initially inverted so as to enable material to be picked up from below the level of the supporting surface for the loader and in which the bucket may be-moved to upright position in any position of the supporting boom.

2,811,265 Patented Oct. 29, 1957 Other objects and advantages will appear in the fol lowing description of the preferred embodiment of the invention given in connection with the attached drawings, of which: V

Fig. 1 is a side elevation of loader of the present in vention showing one side thereof with the bucket in inverted position;

Fig. 2 is a side elevation showing the other side of the loader with the bucket in the same position and with certain of the parts broken away; I I

Fig. 3 is a plan view of the loader with the bucket in upright position; I V i Fig. 4 is a diagrammatic side view of the loader show; ing the bucket or scoop inverted and in its lowermost position;

Fig. 5 is a view similar to Fig. 4 showing the bucket partially moved toward its upright position;

. Fig. 6 is a view similar to Fig. 4 showing the bucket in its upright position with the boom in its lowermost position; v

Fig. 7 is a view similar to Fig. 4 showing the bucket in an upright position and also the boom in an elevated position;

Fig. 8 is a schematic diagram showing the hydraulic system for the various hydraulic actuators; and p Fig. 9 is a fragmentary view similar to Fig. 8 showing a modified hydraulic system.

Referring more particularly to the drawings, the loader of the present invention includes a self-propelled vehicle having a rear or motor containing section 1 0 and a front or boom supporting section 12.; The vehicle is ofthe type which is steered by pivoting the two sections 10 and 12 about a vertically extending axis provided by the pivots 14, the section 12 also pivoting about a horizontal axis with respect to the rear section 10 by means of a sleeve 16 (Fig. 2) forming part of a yoke member 18. The yoke member 18' is pivotally connected to the rear section 10 by the pivots 14 for movement about a verticalaxis and its sleeve 16 is journaled in another sleeve 20 secured to and forming part of the front section 12. Hydraulic actuators (notshown) under control of a steeringwheel (also not shown) positioned in the cab 22 of the vehicle and operating through piston rods 24 (Fig. 3) steer the vehicle. v The'vehicle is provided with rear wheels 26 and front wheels 28, all of which are driven from a motor (not shown) mounted in the rear'section 10, the drive to the front wheels 28 being through a shaft 30 provided with universal joints therein and extending through the sleeve 16 of the yoke member 1 i i a The front section 12 of the'vehicle has upstanding side members 32 and 34 (Fig. 2) secured to the axle housing 35 thereof and to the sleeve 20, the side members being of generally triangular shape with the base of the triangle extending longitudinally of the vehicle. A boom 36 of tubular formvhas laterally extending reinforcing portions 38 at its rear end. Tubular bearing portions 40 are secured to the reinforcing portions 33 and are journaled on a cross shaft 42 secured in and extending between the upper portions of the side members 32 and 34 to provide for raising and lowering the front end of the boom. The boom may be raised and lowered by hydraulic actuators 44'positioned below the boom and connected between a cross shaft 46 extending between the side members 32 and 34 at a point below the cross shaft 42 and a cross shaft 48 extending between a pair of plates 50 secured to and depending from the sides of the boom 36 at a pointspaced from its cross shaft 42, f

The boom also has a bucket supporting structure. '52 pivotallyconnected thereto at its other end, such pivotal connection including reinforcing members 54 and 561cm tending laterally from the boom and haviug' be'aring members 58 secured thereto. The bearing members receive a cross shaft 60 secured in side plates 62 forming part of the bucket supporting structure 52. The' side plates 62 are L-shaped so as to provide two angularly disposed arms and are secured together at their upper eiids by a rear cross plate 64 and top and bottom cross plates 66 and 68, respectively. The side'plates 62 are also secured together at the juncture of their'arms by a tubular member 70 (Fig. 2). A pair of rearwardly extending plates 72 are secured to the rear cross plate 64 and a hydraulic actuator 74 is connected between a cross shaft 76 extending between the plates 72 and a cross shaft 77 extending between a pair of plates 78 secured to and extending upwardly from the boom 36 at a point spaced from the cross shaft 60. It will be apparent that the actuator 74 may be employed to pivot the bucket supporting structures 52 about the cross shaft 60.

The lower arms of theside plates '62 of the bucket supporting structure 52 are curved so as to provide a concave upper edge toreceive the convex bottom portion 80 of a bucket orscoop which has apair of plates 84 secured to and extending itsfront surface when the bucket is in an upright position, the plates 84 being adjacent the bottom of the bucket. The ends of the lower arms of the side plates 62 of the bucket supporting structure are pivotally connected to the plates 84 by means of a cross shaft 86, the cross shaft being positioned adjacentthe lower front portion of the bucket. The

In order to prevent such rearward tipping of the bucket 82, for example, during raising of the boom from the position shown in Fig. 6 to that shown in Fig. 7,- the actuator 74 for moving the bucket supporting structure 52 relative to the boom 36 is controlled to automatically maintain the bucket supporting structure 52 and the bucket 82 in an upright position. This is accomplished by employing a valve coiit'rol rod 108 (Fig. 2) having one end connected to a valve actuating lever 110 and the other end connected through a lost motion device, such as a chain 112, to the tubular member 70 joining the side plates 62 of the bucket supporting structure 52. The lever 110 is pivoted at 11 4 to the side member 34 of the front vehicle section 12.and is urged in a clockwise direction in Fig. 2 by a tension spring 116, the movement of the lever being restrained by stops 1 18 also carried by the side member 34. The lever 110 is connected to a control valve 120 which is mounted on the side member 34 andwhich controls communication between the piston chambers at the opposite ends of hydraulic actuator '74.

The end. of the valve control rod 108 opposite the lever 110 is supported in a guide 122 (Fig. 1) carried by one of the plates 50 depending from the boom 36 so that the valve control rod l08. andchain 112 in conjunction with tubular member 70 extending between the side plates 62 of the bucket supporting structure 52 has secured thereto a pair of rearwardly extending plates 88, one of which is shown in Fig. 2 and both of which are shown in Fig. 3. The'plates 88 are spaced laterally from each other and a hydraulicractuator 90 is connected between a cross pin 91 extending between the rear ends of the plates 88 and a cross pin 92 positioned within a slot 94 in the bottom of the bucket 82. The slot. 94 extends through a housing 96 in the bucket, interior, as shown in Figs. 2 and 3, and the side portions of the housing support the ends of the pin 92 The slot 94 is of sufiicient width to receive the eiid of the actuator 90 and it will be apparent that the actuator 90 may be. employed to tip the'bucket relative to the bucket supporting structure from the positions shown in Figs. 2 or 4, to a retracted position shown in Figs. 6 and 7 in which the rear and bottom walls. of the bucket engage the edges of the side plates 62 of the bucket supporting structure.

A latch 98 (Fig. 2) is provided for holding the bucket 82 in its retracted position in its supporting structure 52. The latch 98 is of hell crank form and is pivoted inter,- mediate its ends on a pivot pin 100 extending between the plates 72. One end of the latch is adapted to extend upwardly through a suitable aperture 102 in a reinforcing plate secured to the rear upper portion of the bucket and is adapted to be retracted from such position by a small hydraulic actuator 106. The actuator is of the type which causes its plunger to be projected when hydraulic fluid under pressure is supplied to the actuator, the plunger being spring returned when the hydraulic pressure isreleased. The hydraulic actuator 106 is actuated to release the latch 98 fromengagement with the plate 104 of the bucket whenever hydraulic fluid under pressure is supplied to the rear. end of the actuator 90 to pivot the bucket about its.cross shaft 86.

' The loader also includes structure for preventing the bucket supporting structure 52 from being pivoted in a counterclockwise direction in Figs. 6 and 7 past a position in which the upper legs of the L-shaped side plates of the bucket supporting structure 52 are substantially vertical. That is to say, the bucket supporting structure 52 may be pivoted in a clockwise direction in Figs. 6 and .7 by the actuators 74 at any time but the bucket supporting structureSZ can not be pivoted in' a counterclockwise directio .to position in whichthe bucket carriedthereby is r aitwa d td a sl, th 'v ethe bucket supporting structure 52 and the boom 36 provide an approximate parallelogram or parallel linkage arrangement when the chain 112 is straightened, i. e., when the. bucket supporting structure 52 and bucket 82 are in an upright position. This parallelogram arrangement is illustrated in Figs. 6 and '7. It will be appreciated that the weight of the. bucket 82 and the bucket supporting structure 52 is positioned relative to the cross shaft 60 so that gravity tends to pivot the bucket supporting structure in a clockwise direction in Figs. 6 and 7 about the cross shaft 60. Raising of the boom from the position shown ii Fig. 6 to that shown in Fig. 7 would, however, tip the bucket toward the vehicle unless the actuator piston rod 123 ofthe actuator is moved outwardly of the actuator. To prevent such rearward tipping of the bucket supporting structure 52 and bucket 82 toward the vehicle, it is merely necessary to establish communication between the opp'osite'ends of the hydraulic actuator 74 whenever the chain 112 'is'tensioned and this is accomplished by the valve which is actuated by movement of the lever 110,

A suitable hydraulic control system for the actuators 44, 7.4-and 90, aswell as the latch control actuator 106, is shown in Fig. 8. Such system has a source of hydraulic oil under pressure, including an oil supply tank 124, a pump 126 and a pressure releasevalve 128. Such source supplies hydraulic fluid under pressure through a conduit 130 to a valve unit 131 having acontrol lever 132 for the hydraulic actuators 44, a control lever 134 for the hydraulic actuators 74 and a control lever 136 for the hydraulic actuator 90. The control valve unit 131 may be of any known or suitable type having four-way valves controlled-by the levers 132, 134 and 136 each of which will admit hydraulic fluid from the pump 126 to one end of its associated hydraulic actuator while exhausting it from the other to drive its piston rod one way or the other, depending upon the direction a corresponding control lever is moved from a neutral position. It will be apparent that the boom 36 may be raised and lowered by the actuators 44 under control of the lever 132; that the carriage supporting structure 52 may be rocked about its cross shaft 60 with respect to the end of theboom 36 by the actuator 74 under control of the lever 136 and that the bucketISZ may be pivoted about its cross shaft 86 with respect to the bucket supporting structure 52 by the actuator 90 under control'of the lever 136.

The valve 120, actuated by the rod 10,8 and lever 110, is connected across the conduits 1.38 and 140 supplying hydraulic fiuidto the actuator 74. Whenever the chain 112Qis :tensionedtocause the valve control rod 108 to actuatevalve120, communication is established between the conduits 138 and 140. This allows the piston rod 123 of the actuator 74 to be withdrawn from the actuator 74 by the weight of the bucket 82 and bucket supporting structure 52. The bucket supporting structure thus pivots in a clockwise direction in Figs. 6 and 7 relative to the boom until tension on the chain 112 is released. Since the change in volume of the piston chamber at the piston rod end of the actuator 74 for a given movement of the piston rod is somewhat less than the change in volume of the piston chamber at the other end of the actuator, less hydraulic fluid will flow out of the piston rod end of the actuator 74 through the conduit 38 than is required to flow into the other end of the actuator through the conduit 140. In order to supply the requisite excess fluid, a check valve 144 may be connected between the inlet to the pump 126 and the conduit 140 so as to allow fluid to flow into the conduit 140 through the check valve, but prevent reverse flow. Although, a simple by-pass valve responsive to the angular position of the bucket supporting structure 52 relative to the vehicle, such as the valve 120, may be employed, it is apparent that a four-way valve 145 such as shown in Fig. 9 and of the same type as that controlled by the control lever 134 may be connected in parallel with the valve controlled by the lever 134 in which case hydraulic fluid under pressure will be admitted to the actuator 74 to prevent tipping of the carriage supporting structure 52 and bucket 82 rearwardly past the upright position of Figs. 6 and 7.

The hydraulic actuator 106 for the latch 98 holding the bucket in its retracted position in the bucket supporting structure 52 may, as indicated in Fig. 8, be connected to the conduit 146 leading to one end of the actuator 90. Delivery of hydraulic fluid under pressure from the valve controlled by the control lever 136 into the conduit 146 so as to tend to pivot the bucket about its cross shaft 92 toward its extended position with respect to the bucket supporting structure 52, will cause operation of the actuator 106 to release the latch 98 from the bucket 82. The bucket, when in retracted position in its supporting structure 52, is thus latched in position except when hydraulic fluid is supplied to the actuator 90 in a manner which tends to pivot the bucket away from its supporting structure 52 about the cross shaft 86.

The operation of'the loader of the present invention may be best understood from'Figures 4 to 7, inclusive. In Fig. 4 the boom 36 is shown in its lowest position; the bucket supporting structure52 has been pivoted about its cross shaft 60 to approximately its maximum clockwise tilted position in Fig. 4, and the bucket 82 has been pivoted about its supporting cross shaft 86 to approxi mately its maximum clockwise tilted position. In this position the bucket 82 is directed substantially vertically downwardly. In this position the bucket may be employed to load material or dig a trench below the surface which supports the loader vehicle. Since all of the actuators 44, 74 and 90 are independently operable, a variety of motions may be given to the bucket 82. For example, the boom 36 may be raised and lowered by the actuators 44 to cause the digging edge of the bucket to bite into the material being handled, or the actuator 90 may be employed to movethe bucket 82 from the position shown in Fig. 4 to that shown in Fig. 5 in order to cause loading of the bucket, for example, from a trench being dug. The actuator 74 may be employed to move the bucket 82 from the position shown in Fig. 5 to that shown in Fig. 6 by pivoting the bucket supporting structure 52 about its supporting cross shaft 68. 1

When the bucket supporting structure 52 reaches the position shown in Fig. 6, the chain 112 is tensioned to cause the valve 120 to be opened and prevent further pivotal movement of the bucket supporting structure 52 in a counterclockwise direction. The actuators 44 may be operated to raise the boom 36 and during such movement, the bucket supporting structure 52 and bucket 82 are' maintained by the valve 120 in an upright posi- 6 tion in their movement from the position shown in Fig. 6 to that shown in Fig. 7 by the control afforded by the valve 120. The bucket may, however, be tipped in a clockwise direction in Figs. 5 to 7 relative to the bucket supporting structure at any time by the actuator and the bucket supporting structure may likewise be tipped relative to the boom by the actuator 74 in a clockwise direction at any time. Thus, the bucket can be dumped by Using either actuator 74, or actuator 90, or both, and can be positioned in any desired position for loading. For example, the position shown in Fig. 5, or positions'with the boom slightly raised above that shown in Fig. 5, or in which the bucket supporting structure 52 is rotated somewhat counterclockwise from that shown in the figure may be employed for loading from the surface or from a pile of material. It will also be apparent that the vehicle may be driven forwardly to assist in any loading operations and may be steered by pivotal movement between the rear and front sections 10 and 12, respectively, of the vehicle during the loading operation. It will be apparent that an extremely flexible loading device has been provided, suitable for handling various types of material, and enabling loading to be done even below the surface upon which the loader vehicle rests, while at the same time, enabling the bucket to be carried to a relatively high elevation and dumped.

I claim:

1. A loader comprising a vehicle, a boom having one end thereof pivotally connected to said vehicle to provide for raising and lowering said boom, a bucket structure including a bucket, said structure being pivotally connected to the other end of said boom for movement about an axis extending laterally of said boom, power means connected between said boom and said vehicle to raise and lower said boom, power means connected between said boom and said structure for pivotally moving said'structure about said axis through a range of movement providing for supporting said bucket in an upright position in any position of said boom including the lowermost position of said boom and in positions in which said bucket is tipped away from said vehicle, and means controlled by the angular position of said structure relative to said vehicle to prevent the last mentioned power means from moving said structure to a position in which said bucket is tipped toward said vehicle.

2. A loader comprising a vehicle, a boom having one end thereof pivotally connected to said vehicle to provide for raising and lowering said boom, a bucket structure including a bucket, said structure being pivotally connected to the other end of said boom for movement about an axis extending laterally of said boom, power means connected between said boom and said vehicle to raise and lower said boom, power means including a hydraulic actuator having a piston chamber at each end thereof and connected between said boom and said structure for pivotally moving said structure about said axisthrough a range of movement providing for supporting said bucket in an upright position and in positions in which said bucket is tipped away from said vehicle, and means controlled by the angular position of said structure relative to said vehicle for controllably establishing communication between said chambers to prevent the last mentioned power means from moving said structure to a position in which said bucket is tipped toward said vehicle.

3. A loader comprising a vehicle, a boom having one end thereof pivotally connected to said vehicle to provide for raising and lowering said boom, a bucket struc ture including a bucket, said structure being pivotally connected to the other end of said boom for movement about an axis extending laterally of said boom and said bucket being pivotally connected to said structure for movement between a retracted position and extended positions in which said bucketis tipped away from said vehicle reiative to said structure, power means connected between saidboomand said vehicle to raise and lower said boom, second power means connected between said boom'and said structure for pivotally moving said structure about said axis to move said bucket when in said retracted position in said structure between an upright position in any position of said boom including the lowermost position of said boom and positions in which said bucket when in said retracted position is tipped'away from said vehicle, third power means connected between said structure and said bucket to move said bucket relative to said structure between said retracted position and said extended positions, and means controlled by the angular position oi said structure relative to said vehicle to prevent said second power means from moving said structure to a position in which said bucket is tipped toward said vehicle when said bucket is in said retracted position.

4, A loader comprising a vehicle, a boom having one end thereof pivotally connected to said vehicle to provide for raising and lowering said boom, a bucket structure including a bucket, said structure being pivotally connected to the other end of said boom for movement about an axis extending laterally of said boom and said bucket being pivotally connected to said structure for movement between a retracted position and extended positions in which said bucket is tipped away from said vehicle relative to said structure, power means connected between said boom and said vehicle to raise and lower said boom, second power means connected between said boom and said structure for pivotally moving said structure about said axis to move said bucket when in said retracted position in said structure between an upright position in any position of said boom includingthe lowermost position of said boom and positions in which said bucket when in said retracted position is tipped away from said vehicle, third power means connected between said structure and said bucket to move said bucket relative to said structure between said retracted position and said extended positions, means controlled by the angular position of said structure relative to said vehicle to prevent said second power means from moving said structure to a position, in which said bucket is tipped toward said vehicle when said bucket is in said retracted position, latch means for holding said bucket in retracted position in said structure, and means responsive to the actuation of said third power means to release said latch means when said third power means is actuated to move said bucket from said retracted position.

5. A loader comprising a vehicle, a boom having one end thereof pivotally connected to' said vehicle to provide for raising and lowering said boom, a bucket structure including a bucket, said structure being pivotally connected to the other end of said boom for movement about an axis extending laterally of said boom and said bucket being pivotally connected to said structure for movement between a retracted position and extended positions in which said bucket is tipped away from said vehicle relative to said structure, power means connected between said boom and said vehicle to raise and lower said boom, second power means connected between said boom and said structure for pivotally moving said structure about said axis to move said bucket when in said retracted position in said structure between an upright position and positions in which said bucket when in said retracted position is tipped away from said vehicle, third power means connected between said structure and said bucket to move said bucket relative to said structure between said retracted position and said ex tended positions, and means controlled by the angular position of said structure relative to said vehicle to prevent said second power means from moving said structure to a position in which said, bucket is tipped toward said vehicle when said bucket is in said retracted position, the ranges of movement of said bucket relative to said structure and of said structure relative ,to said boom being sufiicient to provide for movement ofisaid bucket from said upright position to an inverted position in any position of said boom including the lowermost position of said boom.

6. A loader comprising a vehicle, a boom having one end thereof pivotally connected to saidvehicle to provide for raising and lowering said boom, a bucket supporting structure including a bucket, said structure being pivotally connected to the other end of said boom for movement about an axis extending laterally of said boom, said bucket being pivotally connected to said structure for pivotal movement about an axis extending laterally or" said boom, first hydraulic-actuator power means connected between said boom and said vehicle to raise and lower said boom, second hydraulic actuator power means connected between said bucket and said structure to pivot said bucket between a retracted position in said structure-and extended positions in which said bucket is tipped away from said vehicle relative to said structure, third hydraulic actuator power means connected between said boom and said structure for pivotally. moving said structure about said axis to move said bucket when in retracted position between an upright position and positions in which said bucket is tipped away from said vehicleand means controlled by the angular position of said structure relative to said vehicle to prevent said third power means from moving said structure to a position in which said bucket is tipped toward said vehicle;

7. Aloader comprising-a vehicle, a boom having; one end thereof-pivotally connected to: said vehicle to providefor raising and lowering said-boom, a bucket structure including a bucket, said structure being pivotally connectedto the other end of said boom for; movement about an axis extending laterally of saidboom, power means connected between said boom and said vehicle to raise and lower said-boom, power means connected between said boom and said structure for pivotally moving said structure about said axis through a range. of movement, providing for'supporting said bucket in an uprightpositionin any position of said boom including the lowermost position of said boom and in positions in which said bucket is tipped awaynfrom said vehicle, and automatic means controlled by the angular position of said structure relative to said vehicle to prevent the last mentioned power means from moving saidstructure to a position in which said bucket is tipped toward'said vehicle, saidautomatic means including a parallel linkage having a lost motion device therein for actuating a control for said last mentioned power means when said structurev tends to assume a positionin which said bucket in said retracted position would be tipped toward said vehicle. 8. A leader comprising a vehicle, a boom having one end thereof pivotally connected to said vehicle toprovide fo r raising 'and lowering said boom, a bucket supporting structure including a bucket,- said structure being pivotally connected to the other end of said boom for movement about an axis extending laterallyof said boom, said bucket being pivotally connected to said structure for pivotal movement about an axis extending laterally of said boom, first hydraulic actuator powermeans connected between said boom and said vehicle tovraise and lower said boom, second hydraulic actuator power means connected between said bucket and said structure to pivot' said bucket between a retracted position in said structure and extended positions in which said bucket is tipped away from said vehicle relative to said structure, third hydraulic actuator power means connected between said boom and said structure forpivotally mov- 9 ing said structure about said axis to move said bucket when in retracted position between an upright position and positions in which said bucket is tipped away from said vehicle, and automatic means controlled by the angular position of said structure relative to said vehicle to prevent said third power means from moving said structure to a position in which said bucket is tipped toward said vehicle, said automatic means including a link having a lost motion device therein and connected between said vehicle and said structure for actuating a hydraulic 10 valve controlling said third power means when said structure tends to assume a position in which said bucket in said retracted position would be tipped toward said vehicle.

References Cited in the file of this patent UNITED STATES PATENTS 2,707,056 Gerst Apr. 26, 1955 

